1. Field of the Invention
The present invention relates to a high-performance zoom lens system which is used in a small imaging apparatus employing an image sensor, such as a CCD (charged coupled device), which has been utilized in a digital still camera and the like.
2. Description of the Prior Art
In recent years, various kinds of zoom lens systems which have been used in imaging apparatus of digital still cameras have been proposed. For example, by effectively providing at least one aspherical lens surface (hereinafter, an aspherical surface) made of a resin material, a compact zoom lens system having a high resolution and minimum amount of distortion, and having a small number of lens elements has been known in the art, e.g., as disclosed in Japanese Unexamined Patent Publication No. 2003-057542.
However, the zoom lens system explained above has room for improvement, if an attempt is made to apply such a zoom lens system to an imaging device of a thin digital still camera. Namely, the overall length of the conventional zoom lens system is too long during use and even in a fully retracted state.